1. Field of the Invention
The present invention relates to a signal reading apparatus and an image pickup system using the signal reading apparatus.
2. Description of the Related Art
Examples of a signal detection apparatus for detecting a magnetic signal or the like include a photoelectric conversion apparatus for detecting a light. Representative types of this photoelectric conversion apparatus are a CCD type photoelectric conversion apparatus and a MOS type photoelectric conversion apparatus. The MOS type photoelectric conversion apparatus is provided with a pixel unit in which pixels that are unit cells each including a photoelectric conversion element such as a photo diode are arranged two-dimensionally, a capacitance unit for holding a signal from the pixel unit, and a common signal line for outputting a signal from the capacitance unit to the outside.
Japanese Patent Laid-Open No. 2005-020483 discloses a configuration where a plurality of common signal lines are provided and multiplexed. In addition, Japanese Patent Laid-Open No. 2005-086260 discloses a configuration where a capacitance unit is formed into a block for reading.
As disclosed in Japanese Patent Laid-Open No. 2005-020483, by providing the plurality of common signal lines, the speed of reading data is improved. However, an offset due to a variation in the common signal lines may be caused. Furthermore, in a case where the plurality of common signal lines are provided, the number of amplifiers provided to output units is also increased. Thus, the power consumption is increased. Also, depending on a relation with respect to the outside of the photoelectric conversion apparatus, the number of output terminals required for the photoelectric conversion apparatus may be limited in some cases.